Atkins Shakes... LUMPY ?!

I can;t find a ready made strawberry that taste any good, I make my own with real strawberries.

I sometimes drink the Oh Yeah! brand RTD (chocolate... yummy!) and I have occasionally gotten one that is lumpy.  I have no idea what causes them to get that way (an internet search at one point yielded NOTHING), but because I don't know -- and therefore am not sure that it isn't "bad" even though it isn't near the expiration date -- and because it turns my stomach just thinking about it, I either throw those away or return them to the store. (Unfortunately, if you buy them by the case, you have to return the entire case and then take your chances on the next case being ok!)

Lora